1. Field of the Invention
The present invention is directed to an axle assembly in a drive device for the road wheels of a vehicle, the axle assembly having a stationary housing configured to house a differential unit and axle housings through which axles are arranged. The interior of the stationary housing is partially filled with a lubricating liquid, and a rotatably drivable driveshaft is inserted into the housing interior. The driveshaft carries a driving gear wheel at the end of the driveshaft which extends into the interior of the stationary housing. A differential unit having a crown wheel and a differential housing are arranged in the stationary housing. The crown wheel is rotatably bearing-mounted in the stationary housing and is rotatably driven by the driving gear wheel. The crown wheel rotatably drives a plurality of differential gear wheels of the differential unit. Driven gear wheels are rotatably driven in turn by these differential gear wheels. The driven gear wheels are drivingly connected in each instance to driven axle shafts for driving the road wheels of the vehicle. A venting bore is provided in an axle housing of the axle assembly for venting air.
2. Background of the Invention
A drive device, of the type mentioned above, is shown highly schematically in FIG. 1. As shown in the figure, an axle assembly 1 receives a rotating driveshaft 3 and converts the rotational motion of the driveshaft 3, powered by the drivetrain 4, into rotational motion of the axles 5 to drive the wheels 7 of the vehicle. The axle assembly 1 has a generally spherical centrally disposed stationary housing 10, the interior 9 of which is configured to house a differential unit 16. Axle housings 20, through which the axles 5 are disposed, extend from each side of the stationary housing 10.
The driveshaft 3 is guided into the interior 9 of the stationary housing 10 approximately horizontally. At its end the driveshaft 3 carries a driving gear wheel 12, which is formed as, for example, a bevel gear configured to mesh with a crown wheel 14 of a differential unit 16 arranged in the stationary housing 10. The crown wheel 14 is likewise formed as a bevel gear.
It is known for the differential unit 16 to be at least partially immersed in the lubricating liquid in the interior 9 of the stationary housing 10. In conventional stationary housings 10, lubricating liquid is sprayed throughout the stationary housing 10 by the rotational relative motion of various gears and bearings in the differential unit 16, for example by the movement of the crown wheel 14 and the driving gear wheel 12.
A conventional stationary housing 10 of an axle assembly 1 is shown in FIG. 2, without showing the components of the driving gear wheel 12, crown wheel 14, the differential unit 16 and the axles 5. The stationary housing 10 joins, at each side, with axle housings 20, through which the axles 5 pass towards the wheels 7.
A venting bore 22 is provided in one of the axle housings 20. The venting bore 22 allows pressurized air to escape upon excessive buildup of such air, which may occur, for example, due to an increase in the temperature of the lubricating liquid. Differential supports 23 are formed on interior walls of the stationary housing 10 and provide support for the differential unit 16.
The conventional axle assembly 1 has the disadvantage that the lubricating liquid sprayed by the moving components housed in the stationary housing 10 tends to travel toward an area of an oblique inner wall of the stationary housing 10 close to where the axle housing 20 having the venting bore 22 joins the stationary housing 10. This area, which will hereinafter be referred to as an axle bracket, identified by reference numeral 24 in FIG. 2, is located close to the venting bore 22, such that lubricating liquid that splashes on the axle bracket 24 flows along the interior contour of the stationary housing 10 and the axle bracket 24 to the venting bore 22, from which the lubricating liquid can escape.
That is, the splashing of the lubricating liquid by the rotary components of the differential unit 16 can lead to the lubricating liquid flowing along the interior of the stationary housing 10 towards the venting bore 22, which can allow the lubricating liquid to escape through the venting bore 22, leading to an uncontrolled loss of lubricating fluid in axle and stationary housings of the axle assembly 1.